Why Do Cats Purr?

By Diana Hutchinson

canstockphoto10982599

Cats purr for many reasons, and it is not always out of contentment. Photo (c) Can Stock Photo

When you hear your cat purr, the common assumption is that your favorite fur ball is feeling quite happy and contented. However, there’s more to purring than just pleasure. One might view purring as similar to a baby’s cry – the sound may be the same but it could indicate anything from hunger to pain to fear.

Even today, the purr remains quite a mystery to cat owners and researchers alike. Purring is the sound produced when cats inhale and exhale in a consistent pattern. Scientists know that the sound is from the intermittent signaling between the muscles of the larynx and the diaphragm. But it remains to be a mystery how the nervous system controls and generates the contraction.

Cats used to be categorized based on their ability to purr or roar. Those who purred were classified by taxonomists as Felinae, while those who roared were under Pantherinae. In the cat family, only four species are capable of roaring, namely: jaguars, leopards, lions, and tigers.

It is impossible for domestic cats to roar as, according to a study by Weissengruber et al. (2002), they do not have the bone located near the larynx known as the hyoid. Roaring cats have a two-piece hyoid bone that is more flexible than the one-piece hyoid in purring cats. No cat can roar and purr at the same time although there is one species, the snow leopard, which cannot roar or purr. Instead it makes a chuffing sound which is between a roar and a purr.

While roars can scare people off with a volume that can reach 114 decibels, a purr sounds more comforting to the human ear as it is only around 25 decibels.

Purring may be associated with contentment and happiness but recent research reveals that it may also be part of a cat’s healing process. Purring has a vibrational frequency of 25 to 140 Hz. In humans, the frequency applied to the surface area in humans for pain relief, wound healing, muscle and tendon repair through Neuromuscular Electrical Stimulation (NMES) is 25 Hz. NMES is a method of rehabilitating muscles through noninvasive and non-addictive means for patients with orthopedic and neurological diagnoses and it uses electrical stimulus to cause muscle to contract.  At more than 30 Hz, the frequency is believed to strengthen the muscles as explained by Hinchcliff, Andris, & Raymond (2013, p.1,236).

Cats often purr when in pain or in a stressful situation. If you pay attention to your cat’s vocalization, you might notice that he purrs when he is recovering from an injury. After playing and chasing, cats often purr which could be their way to relieve sore and stretched muscles. Another example are cats that are about to give birth; the mother cat may purr before and after contractions perhaps as a way of recovering from the pain of giving birth. At the same time, it is believed that purring also helps kittens grow stronger bones, according to a 2013 study by Hart & Hart (2013, p. 123).

An interesting study by Qureshi et al. (2009) revealed that the healing powers of a purr could be effective in humans too. The University of Minnesota Stroke Center’s findings show that a person with at least one cat is 40 per cent less likely to have a stroke.

Purring Ties a Kitten to Its Mother

In cats that have just given birth, purring could also serve as the main source of communication between the mother cat and the kitten. Kittens are born blind and deaf and the best way that they can find their mothers is by purring. Kittens learn how to purr just a few days after they are born. Through purring, they can find their mother and their mother knows where they are.

Research has revealed that the purring sound that domestic cats make when they are hungry and not are distinctive. The “solicitous purr” that cats can make is designed to make humans pay attention to their needs as found out in a study (2009) conducted at the University of Sussex, England by Dr. McComb and her team.

Cats Purr When They Fear Something

Going to the vet can be a stressful experience for your feline and you might hear him purring in the clinic because he is fearful.

A trip to the vet involves getting your cat into a cat box and unless he is used to trips where he has to be in a confined space, he could feel scared and afraid. Do remember that cats often dislike being enclosed in a small space where they can’t move around.

If you notice that your cat is purring more than he usually does during visit to the vet, it may be his way of staying calm. Fortunately, vets are trying to address the stress that these visits have on cats. There are Fear Free certified practitioners who are schooled in the art of providing a stress-free environment to cats.

If you thought that your kitty is looking forward to a visit to the clinic because he is purring a lot, you may be wrong. You can also get clues from your cat’s behavior to know if it is a happy, “nice to see you doc” purr or a purr than means that your kitty needs reassurance that the visit is going to be all right.

Purring is a Feline Thing

While purring can mean many things, there is nothing more delightful than when your favorite kitty is on your lap making melodic sounds. Although many studies are being conducted to decode the meaning behind every purr cat owners still have the advantage over science –they know their cats through and through.

At the end of the day, people whose cats rule their worlds would most likely agree that, in the end, the science behind purring does not matter all that much. The important thing to them is that their cats are content, and purring is a way of showing this.

References

Hart, B., & Hart, L. (2013). Your Ideal Cat: Insights into Breed and Gender Differences in Cat Behavior. West Lafayette, IA: Purdue University Press

Hinchcliff, K., Kaneps, A., & Geor, R. (2013). Equine sports medicine and surgery. London, UK: Saunders Elsevier

McComb, K., Taylor, A., Wilson, C., & Charlton, B. (2009). The cry embedded within the purr (1st edn.). Current Biology 19(13):R507-8 

Qureshi, A., Memon, M.Z., Vazquez, G. & Suri, M.F.K. (2009). Cat ownership and the Risk of Fatal Cardiovascular Diseases. Results from the Second National Health and Nutrition Examination Study Mortality Follow-up Study

Weissengruber, G., Forstenpointner, G., Peters, G., Kubber-Heiss, A., & Fitch, W. (2002). Hyoid apparatus and pharynx in the lion (Panthera leo), jaguar (Panthera onca), tiger (Panthera tigris), cheetah (Acinonyx jubatus) and domestic cat (Felis silvestris f. catus). Journal of Anatomy, 201(3), 195-209

Diana Hutchinson is a pet owner member of the Pet Professional Guild and the founder of Tinpaw.com.

 

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2 Responses to Why Do Cats Purr?

  1. Karen.l.wylie@gmail.com' Karen says:

    My cat purred, in a very strange, almost guttural, way, in the two days before his death. He died of lymphoma when he was 12 years old. It was the strangest purr I’d ever heard, and seemed to signal extreme pain and fear. It was an awful purr that I’ll never forget.

  2. Kittens often purr to when they are only few days old to tell their mother that they are OK.

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